libguestfs does not depend on an x86 architectural feature.
qemu-system-x86_64 emulates a PC, and PCs don't have -kernel. We
should discourage people from depending on this interface for
production use.

I really don't get this whole thing where we must slavishly
emulate an exact PC ...

History has shown that when we deviate, we usually get it wrong and it
becomes very painful to fix.